hooks: torch: add support for MKL-enabled torch builds

Add support for MKL-enabled `torch` builds on Windows (e.g., the
nightly `2.3.0.dev20240308+cpu` build). The `torch` hook now
attempts to discover and collect DLLs from MKL and its dependencies
(`mkl`, `tbb`, `intel-openmp`).

This should prevent frozen program from silently crashing due to
missing MKL DLLs, which slip past PyInstaller's binary dependency
analysis due to being dynamically loaded at run time.

news/712.update.rst

@@ -0,0 +1,4 @@
+Update ``torch`` hook to add support for MKL-enabled ``torch`` builds
+on Windows (e.g., the nightly ``2.3.0.dev20240308+cpu`` build). The hook
+now attempts to discover and collect DLLs from MKL and its dependencies
+(``mkl``, ``tbb``, ``intel-openmp``).

src/_pyinstaller_hooks_contrib/hooks/stdhooks/hook-torch.py

@@ -10,6 +10,8 @@
 # SPDX-License-Identifier: GPL-2.0-or-later
 # ------------------------------------------------------------------
 
+import os
+
 from PyInstaller.utils.hooks import (
     logger,
     collect_data_files,
@@ -20,7 +22,7 @@
 )
 
 if is_module_satisfies("PyInstaller >= 6.0"):
-    from PyInstaller.compat import is_linux
+    from PyInstaller.compat import is_linux, is_win
     from PyInstaller.utils.hooks import PY_DYLIB_PATTERNS
 
     module_collection_mode = "pyz+py"
@@ -70,6 +72,63 @@ def _infer_nvidia_hiddenimports():
             nvidia_hiddenimports = []
         logger.info("hook-torch: inferred hidden imports for CUDA libraries: %r", nvidia_hiddenimports)
         hiddenimports += nvidia_hiddenimports
+
+    # The Windows nightly build for torch 2.3.0 added dependency on MKL. The `mkl` distribution does not provide an
+    # importable package, but rather installs the DLLs in <env>/Library/bin directory. Therefore, we cannot write a
+    # separate hook for it, and must collect the DLLs here. (Most of these DLLs are missed by PyInstaller's binary
+    # dependency analysis due to being dynamically loaded at run-time).
+    if is_win:
+        def _collect_mkl_dlls():
+            import packaging.requirements
+            from _pyinstaller_hooks_contrib.compat import importlib_metadata
+
+            # Check if torch depends on `mkl`
+            dist = importlib_metadata.distribution("torch")
+            requirements = [packaging.requirements.Requirement(req) for req in dist.requires or []]
+            requirements = [req.name for req in requirements if req.marker is None or req.marker.evaluate()]
+            if 'mkl' not in requirements:
+                logger.info('hook-torch: this torch build does not depend on MKL...')
+                return []  # This torch build does not depend on MKL
+
+            # Find requirements of mkl - this should yield `intel-openmp` and `tbb`, which install DLLs in the same
+            # way as `mkl`.
+            try:
+                dist = importlib_metadata.distribution("mkl")
+            except importlib_metadata.PackageNotFoundError:
+                return []  # For some reason, `mkl` distribution is unavailable.
+            requirements = [packaging.requirements.Requirement(req) for req in dist.requires or []]
+            requirements = [req.name for req in requirements if req.marker is None or req.marker.evaluate()]
+
+            requirements = ['mkl'] + requirements
+
+            mkl_binaries = []
+            logger.info('hook-torch: collecting DLLs from MKL and its dependencies: %r', requirements)
+            for requirement in requirements:
+                try:
+                    dist = importlib_metadata.distribution(requirement)
+                except importlib_metadata.PackageNotFoundError:
+                    continue
+
+                # Go over files, and match DLLs in <env>/Library/bin directory
+                for dist_file in dist.files:
+                    if not dist_file.match('../../Library/bin/*.dll'):
+                        continue
+                    dll_file = dist.locate_file(dist_file).resolve()
+                    mkl_binaries.append((str(dll_file), '.'))
+
+            logger.info(
+                'hook-torch: found MKL DLLs: %r',
+                sorted([os.path.basename(src_name) for src_name, dest_name in mkl_binaries])
+            )
+            return mkl_binaries
+
+        try:
+            mkl_binaries = _collect_mkl_dlls()
+        except Exception:
+            # Log the exception, but make it non-fatal
+            logger.warning("hook-torch: failed to collect MKL DLLs!", exc_info=True)
+            mkl_binaries = []
+        binaries += mkl_binaries
 else:
     datas = [(get_package_paths("torch")[1], "torch")]